As semiconductor devices scale to smaller dimensions, non-planar transistors are increasingly attractive as alternatives to planar transistors due to the limits on scalability imposed by planar transistor geometry. For example, so-called fin field effect transistors (finFET) have been deployed in complementary metal oxide semiconductor (CMOS) technology for the 22 nm device generation. A finFET is a type of three dimensional (3-D) transistor in which a narrow strip of semiconductor material (fin) that extends vertically from a main substrate surface is used to form source/drain (S/D) and channel regions of the transistor. A transistor gate is then deposited to wrap around opposite sides of the fin thereby forming a gate structure that bounds multiple sides of the channel.
During processing to form a conventional finFET after etching the semiconductor substrate to define a fin structure, isolation oxide, often referred to as shallow trench isolation (STI) oxide, is deposited. The oxide is then etched back so that that fin structure extends above the oxide to a designed amount according to the desired fin height. Subsequently the exposed fin structure is subject to threshold voltage implants, well implants, punch through stopping implants, and annealing processes. In the replacement gate process for forming a finFET, a further series of processing steps involves deposition of a dummy gate structure, formation of spacers, and deposition of a raised source/drain structure before the dummy gate is replaced via a series of etching and deposition steps with the final gate structure. These process steps entail an extensive thermal budget that may adversely affect the implants performed in early processing steps after the fin formation. Accordingly, resultant device performance of finFETs may be less than desired.
As transistor dimensions scale to even smaller dimensions the above problems may be further exacerbated due to the decreased tolerance for dopant diffusion and dopant loss that may be induced during finFET processing.
It is with respect to these and other considerations that the present improvements are needed.